The present invention relates to an outboard marine drive, and in particular to an engine cover arrangement for an outboard marine drive including an under cover covering a lower part of the engine and defining an upper opening, and an engine cover having a lower opening which closes upon the upper opening of the engine cover via a seal member for jointly defining an engine room.
A relatively large outboard marine drive typically comprises an engine mount case supporting the engine, an under cover attached to the engine mount case to cover a lower part of the engine, and an engine cover having the shape of a deep bowl covering an upper part of the engine. An open upper end of the under cover and an open lower end of the engine cover are joined to each other via a seal member in a detachable manner by means of latch units provided between the under cover and engine cover. The seal member keeps moisture out of the engine room.
The seal member closely engages the interfaces of the under cover and engine cover by being compressed between them under a certain load. If this compressive load is too large, an unacceptably large force is required to latch the engine cover onto the under cover. If the compressive load is too small, the required sealing performance may not be achieved. To meet such a requirement, a seal member including a hollow cross section is proposed, for instance in Japanese patent laid open publication No. 2-292575.
The seal member based on this proposal provides a favorable resiliency which achieves a required performance with a relatively small compressive reaction. However, it still relies on the resiliency of the seal member for the compressive reaction which cooperates with the latch units, and the sealing performance tends to be lost as the seal member has been used for an extended period of time and a substantial part of its resiliency has been lost. To compensate for this problem, lip seals are additionally provided to the seal member. However, the direction of the reaction force is still the same between the hollow part and lip seals, and a sealing performance cannot be maintained once the material of the seal member loses most of its resiliency even with the addition of such lip seals.
In view of such problems of the prior art, a primary object of the present invention is to provide an engine cover arrangement for an outboard marine drive which can provide a favorable sealing performance for an entire service life of the outboard marine drive.
A second object of the present invention is to provide an engine cover arrangement for an outboard marine drive in which the seal member is not directly subjected to the pressure from the latch units or other closure elements.
A third object of the present invention is to provide an engine cover arrangement for an outboard marine drive which does not rely on the resiliency of the seal member for the reaction force of the latch units.
According to the present invention, these objects can be accomplished by providing an engine cover arrangement for an outboard marine drive, comprising: a first cover covering a part of an internal combustion engine and provided with a first opening; a second cover covering a remaining part of the engine and provide with a second opening adapted to be fit onto the first opening, the second cover being provided with a first seal surface extending substantially in parallel with a plane defined by the first and second openings along a peripheral part of the second opening and a second seal surface extending substantially perpendicularly with respect to the first seal surface from an inner periphery of the first seal surface toward the first cover; and a seal member attached along a peripheral part of the first opening of the first cover and adapted to engage both the first and second seal surfaces of the second cover. Typically, the seal member comprises a retaining portion attached to an edge of the first cover, and an engagement portion extending from the retaining portion. In particular, in a larger outboard marine drive, the engine itself is typically mounted on an engine mount case made of metallic member, and the second cover consists of an under cover fixedly attached to the engine mount case while the first cover consists of an engine cover. The under cover and engine cover are typically made of plastic material.
Because the seal member attached along a peripheral part of the first opening of the first cover is adapted to engage not only a first sealing surface perpendicular to the closing direction of the two covers but also a second sealing surface substantially in parallel with the closing direction of the two covers, the seal member is not required to rely on the pressure directed in the closing/opening direction of the two covers, and is prevented from being excessively compressed. Also, by providing a separate stopper arrangement for defining the closed position of the two covers, the seal member is additionally protected from excessive compression.
According to a preferred embodiment of the present invention, the seal member includes a first lip portion engaging the first seal surface and a second lip portion engaging the second seal surface. The lip portions provide a favorably sealing performance without much relying on the pressure acting thereof. The first lip portion is provided in the engagement portion, but the second lip portion may be provided either in the retaining portion or the engagement portion.
According to a particularly preferred embodiment of the present invention, the seal member comprises a first lip portion provided in the engagement portion to engage the first seal surface, a second lip portion provided in the retaining portion to engage the second seal surface, and a third lip portion which extends from the retaining portion next to the first lip portion to engage the second seal surface by being pressed by the first lip portion as the first lip portion engages the first seal surface and deforms inward as a result. The third lip portion may also additionally engage the first seal surface.
Preferably, to enhance such an action of the first lip portion on the third lip portion, the third lip portion may be provided with a cross section having the shape of a laterally facing letter-V or chevron with a concave side facing the first lip portion, and the first lip portion may be provided with an arcuate cross section with a concave surface facing the third lip portion.